Mark Haddon was born in Northampton and educated at Uppingham School and Merton College, Oxford, where he studied English.

In 2003, Haddon won the Whitbread Book of the Year Award and in 2004, the Commonwealth Writers' Prize Overall Best First Book for his novel The Curious Incident of the Dog in the Night-time, a book which is written from the perspective of a boy with Asperger syndrome. Haddon's knowledge of Asperger syndrome, a condition on the autism spectrum, comes from his work with autistic people as a young man. In an interview at Powells.com, Haddon claimed that this was the first book that he wrote intentionally for an adult audience; he was surprised when his publisher suggested marketing it to both adult and child audiences.

His second adult novel, A Spot of Bother, was published in September 2006, and The Red House in 2012.

Mark Haddon is also known for his series of Agent Z books, one of which, Agent Z and the Penguin from Mars, was made into a 1996 Children's BBC sitcom. He also wrote the screenplay for the BBC television adaptation of Raymond Briggs's story Fungus the Bogeyman, screened on BBC1 in 2004. In 2007 he wrote the BBC television drama Coming Down the Mountain.

Haddon is a vegetarian, and enjoys vegetarian cookery. He describes himself as a 'hard-line atheist'. In an interview with The Observer, Haddon said "I am atheist in a very religious mould". His atheism might be inferred from The Curious Incident of the Dog in the Night-time in which the main character declares that those who believe in God are stupid.

In 2009, he donated the short story "The Island" to Oxfam's 'Ox-Tales' project, four collections of UK stories written by 38 authors. Haddon's story was published in the Fire collection. (From Wikipedia.)